Hydraulic motors



Feb. 14, 1967 o. ocULE HYDRAULIC MOTORS Filed April 19, 1965 United States Patent O 3,303,749 HYDRAULIC MOTORS Oreste Ocule, Grugliasco, Turin, Italy, assignor to Simit S.p.A., Grugliasco, Turin, Italy Filed Apr. 19, 196s, ser. No. 449,185 Claims priority, application Italy, Apr. 24, 1964, 9,504/ 64 1 Claim. (Cl. 91-175) This invention relates to hydraulic motors having axial free pistons, of the type comprising a rotary block formed with cylindrical recesses extending parallel with the rotational axis of the block. The recesses have pistons slidably mounted therein, which are operated by fluid pressure from a pump and act against a surface inclined to the rotational axis of the block of a swash plate mounted on the stationary motor frame, in order to rotate the latter. Control valves alternately connect each cylinder with the pressure fluid supply pump and exhaust, respectively, dependently upon the angular position cyclically taken by the piston on rotation of the block.

Known hydraulic motors of the abovementioned type afford a limited braking effect when the motor is rotated by effect of the inertia of the driven parts coupled with the rotating motor part. Under these circumstances the pistons are removed from the swash plate against which they normally bear, which results in objectionable hammering and prevents the motor from effectively braking the rotating parts. This process is due to the vacuum set up in the cylinder liners on account of the phase displacement of the piston expansion stroke and pressure fluid supply or of the absence of supply during the said piston stroke.

This necessitates the use of complex brake devices, for the machine parts driven by the motors of the above referred type.

The object of this invention is to provide a hydraulic motor having axial free pistons, wherein the setting up of a subatmospheric pressure in the cylinders is prevented, when an external force raises the number of revolutions to a higher value than that due to the supply of pressure fluid by the pump driving the motor.

According to this invention the axial bore in each piston in which the fluid pressure acts, is connected with a chamber surrounding the rotor and connecting in turn with the fluid reservoir, the communication being established through conduits formed in the piston bottoms, each controlled by a unidirectional valve adapted to automatically close by effect of the fluid acting in the loaded cylinders and open by effect of the vacuum set up in the cylinders when the motor starts being rotated to allow of the fluid at atmospheric pressure to iloW from the reservoir to the axial bore in the pistons and cause the resilient return means acting on the pistons to constantly hold the latter in contact with the swash plate.

Further characteristic features and advantages will be understood from the appended detailed description given by way Iof a non-limiting example, the single figure being 3,303,749 Patented Feb. 14, 1967 Fice A ring 13 is arranged in contact with the flat inner wall of the head portion 1 and is formed with cylindrical projections 13a sealingly engaging through seals 17 the cylindrical recesses 9 in the rotary block. The ring 13 has conduits 14 bored therethrough for supply of fluid pressure to the cylindrical recesses 9 in the rotary block. The

fluid pressure is supplied through an inlet conduit 15 an axial sectional View of a motor according to this invention.

Reference numerals 1 and 2 denoted the head portions of the motor frame, which are connected by rods 3a to a cylindrical housing 3 and are provided with ball or roller bearings 5, 6 and 7 for guiding a shaft 4 arranged on the motor axis. The shaft 4 carries, such as by means of keys 4a a cylindrical block 8 formed with cylindrical recesses 9 extending parallel with the axis, having slidable therein pistons 10 having their outwardly facing end convex and bearing on a ring 11 guided by means of a ball or roller bearing 12 with respect to an internal surface on the head portion 2, which is inclined to the rotational axis of the block 8.

bored in the stationary head portion 1, connecting through a groove 15a in the form of a circular segment cut in the inner face of the head portion 1 with half the cylindrical recesses 9.

The fluid is discharged through a conduit 16 likewise bored in the head portion 1 connecting through a groove 16a cut in the inner face of the head portion with the other half of the cylindrical recesses 9.

The pistons 10 in the recesses connecting with the fluid supply conduit 15 are pressed against the swash plate 11 and act on the rotary block and distributor ring 13 by a tangential thrust which rotates the motor.

According to this invention the pistons 10 are formed with an axial bore 10a opening on the side turned towards the forward head portion 1, accommodating a helical compression spring 18, the opposite ends of which engage two tubular sleeves 19, 20 secured on the cylindrical projection 13a on the ring 13 forming the head portion of the cylinder 9 and to the bottom of the bore 10a in the piston 10, respectively.

A chamber 26 formed by the clearance between the rotor 8 and housing 3 surrounds the rotor 8 and connects through a conduit 27 with a reservoir 30 for the fluid at atmospheric pressure.

The chamber 26 connects with the bore 10a in each piston through an axial opening 21 in the piston bottom and a plurality of holes 22 extending obliquely to the piston axis. The opening 21 connects with the bore 10a in the piston through a larger diameter cylindrical recess 25.

The opening 21 accommodates a unidirectional valve provided with a mushroom head 24 adapted to abut the wall of the recess 25 and with a shank 23 of a size such as to admit of fluid flow through the opening 21 when the head 24 is removed from the recess 25.

During normal operation of the motor, the high pressure acting in each piston effects closure of the valve (23, 24), which intercepts communication between the bore 10a in the piston and drain chamber 26.

When the engine is set in rotation a subatmospheric pressure is set up in the bore 10a in each piston and opens the valve, whereby the fluid in the drain chamber 26 reaches into the bore and releases the subatmospheric pressure. Consequently, the return spring 18 acting on the piston is in a condition to cause the piston to perform its expansion strokes while it is constantly held in contact with the swash plate 11.

Consequently, even when the motor is rotated While the cylinders are not supplied with fluid through the conduit 15, 15a, the fluid fills just the same the bore 10a through the holes 22 in the pistons, and is-subsequently expelled, through the conduits 16a, 16. Consequently, the running motor can be braked by throttling the flow of fluid issuing from the conduit 16 by means of a valve the opening of which is adjustable by the operator.

The device is advantageous in use in connection with motors structurally combined with vehicle wheels for braking on down-hill drive; in control of rotation of towers for cranes, excavators and the like, in which the masses of the rotary parts are considerable and are liable to give rise to undesired movements by inertia.

What I claim is:

A hydraulic motor of the type comprising a tubular body, a rotor rotatably mounted within said body so that a clearance is formed between said body and said rotor,

and a. swash plate situated on one side of the rotor sup-V ported by the body, a plurality of cylindrical recesses parallel to the rotational axis in said rotor, fluid inlet and outlet means disposed adjacent the side of said rotor 0pposite said swash plate, a piston freely slidably mounted in each recess, a compression spring mounted in each recess and urging the piston so that its head abuts said swash plate, a valve housing remotefrom said fluid inlet and outlet means, a conduit in continuous communication with said valve housing and with the clearance between the rotor and the body, a one-Way valve opening towards the inside of the recess mounted in each valve housing and a conduit connecting the clearance between the body and the rotor with a reservoir-,containing uid at atmospheric pressure.

References Cited'by the Examiner UNITED STATES PATENTS 2,667,862 2/1954 AMuller 91-199 2,980,077 4/1961 Magill 9l,-198 3,183,847 5/1965 Raymond 103--173 3,221,660 12/1965 DAmato 103-162 10 MARTIN P. SCHWADRON, Primary Examiner.

PAUL E. MAsLoUsKY, Examiner. 

